North American Turbocoupe Organization



A/F Meter
Spooler87 Offline
Posting Freak
#1
I just hooked up my A/F meter today and have some questions on how it should be running. While the car is idleing, the meter is RAPIDLY fluctuating between full stoich and full lean. Also while driving when i let off the gas the meter will go completely dead until i hit the gas again (then it goes to one bar rich, one bar stoich). Is this how the gage is suppose to operate? If not, how should my gage look while my car is running? Any help would be appriaciated, since I am new to air fuel gages.
All hail Project "Marauder" !
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turbobird63 Offline
Senior Member
#2
Yeah Sounds about right to me, unless you get a wideband that A/F just looks nice.
Christopher Taylor
85 TC, 2.3l, LA3, T3/T4 Turbo 25psi, Stinger FMIC, Forge BOV, Full 3" Exhaust, Esslinger crank pulley- Timing Gears and overdrive WP pulley, BBK 255lph FP, Kirban AFPR, Kirban Shifter, K&N Cone, 3g Alternator, Energy Suspension Bushings throughout, CHE LCA's, Welded SFC's, and TON's of other parts.
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martin0660 Offline
Posting Freak
#3
Sounds about right....

Under decel, throttle closed, the fuel is shut down so it goes blank,

Under cruise, it will quickly swing between lean and the upper part of the scale. Thats the EEC reacting to the A/F ratio in closed loop.

Under boost, the A/F gauge should go to Green, rich.

Those are the two uses I have for these A/F gauges. Under cruise, you can keep it in closed loop for gas mileage. The other is that it will indicate a problem if it doesent go rich under boost.

Bob Myers
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louboy Offline
Member
#4
HEY SPOOLER :I READ IN ONE OF MESSAGES IN THE SEARCH MODE THAT HOOKING THE WIRE UP TO THE #29PIN,ABOUT 6in.UP FROM THE HARNESS IS THE HOT SET UP.CHECK IT OUT. LOU
lou gasson
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trashline Offline
Posting Freak
#5
Yea Idle and cruising speeds the A/F swings to lean rich several times a second. WOT it should obviously go rich.

Apparently the A/F gauge is almost usless on a narrowband sensor. With a wide band you would be able to see the exact ratio and it not "bouncing". This is b/c the narrow bands reads narrower range of A/F ratio mixture.

One good thing about the gauge with a narrow band is it does tell you when your going lean, ie running out of fuel, starving the pump, blown IC hose are some examples. I am always looking at my gauge.
Brian

www.BCPCustom.com

06 Cobalt SS
66 mustang 289 C4 handfully modded

Stingers IC install and tbird photos
http://community.webshots.com/user/trashline
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Jeff K Offline
Administrator
#6
My "useless according to some people" narrow band AF gauge saved my a$$ today..... I always take a quick glance at it when going into boost, especially over 10 psi. As I looked at it, it was full rich, and as boost hit 15, it started to drop way lean. I let off, and then slowly boosted it up while watching my FP gauge. Fuel press increased 1:1 with boost until I hit 13 psi, then fuel press started to rapidly drop to mid 30s psi. CRAP!!

Fuel filter not plugged, and pump seems noisier than usual.... time to drop the tank and have a look.... my guess is either the pump is FUBAR (Walbro 255 HP with only about 40K miles on it Sad ), or the filter sock is plugged. At least the problem happened now, and not in a month and a half while on the road to / from Carlisle!!

This also proves what I have said hundreds of times in posts about fuel problems.... fuel pressure at idle or at cruise tells you almost nothing.... pressure MUST be checked under boost / WOT to show up problems.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Pete D Offline
Administrator
#7
I'm with Jeff. My useless narrow band saved my engine when I forgot to plug the reference line back into the FPR and went out on the back roads for a little test & tune. Needless to say fuel pressure did not rise with boost pressure.
Pete Dunham


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trashline Offline
Posting Freak
#8
I was actually running out of gas when my gauge was running lean so I knew it was time to fill up.

See besides to cool factor it does serve a purpose.
Brian

www.BCPCustom.com

06 Cobalt SS
66 mustang 289 C4 handfully modded

Stingers IC install and tbird photos
http://community.webshots.com/user/trashline
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